In the past, there has been significant breakthroughs in the development of cardiac pacemakers. Such cardiac pacemakers are ones which are programmable and can pace in a variety of pacing modes. The pacemakers can pace in VOO, VVI, VVT, AOO, AAI, AAT, DOO, DVI and DDD modes. Such new and innovative pacemakers come close to simulating the ultimate physiological pacing apparatus. However, there still does exist a great difficulty in determining how a particular implanted pacing apparatus is functioning at any given point in time.
A great majority of diagnostic tools used to evaluate the performance of a cardiac pacemaker have been subordinated to activity which was not seen in real time. Such evaluation was reduced to the production of ECG tapes created by connecting the individual having the implanted pacing apparatus to a series of electrodes so that the ECG tape could be made. After this tape was made, the physician or other technical person would then view the tape using calipers. This inspection would determine whether the proper pacing scheme was being accomplished for the individual having the implanted pacing apparatus (or pacemaker).
In most cases in the past, this evaluation did not take place in real time. It could be hours, days, or even weeks before a proper evaluation could be made as to whether proper pacing was taking place. There has not been any attempts to develop a diagnostic tool which could display a visual representation of the actual pacemaker activity and its associated ECG wave pattern in real time. The major problem in development of such a diagnostic apparatus was centered on the lack of the ability to provide visual representations of sequential cardiac events as seen by the pacing apparatus.
In the past, there has been futile attempts to provide outputs from the pacing apparatus as to mark cardiac events. The events that could not be effectively marked were outputs from the pacer to indicate an atrial or ventricular pulse to cause a depolarization of the cardiac chambers or when the pacing apparatus senses a natural P-wave or R-wave. There were no devices, which over a long period of time could actually provide information indicative of the complete sequence of cardiac events as seen by the pacer.
Coupled with the problems identified in the foregoing paragraphs, there has also been additional problems in determining whether the pacemaker was performing in a manner such that there were proper refractory periods following depolarization of the atrium or ventricle. In cases when the natural refractory period of the heart was not long enough to mask the next cardiac event such as a retrograde R-wave causing depolarization of the atrium, it was not desirable for such atrial depolarization to be detected by the pacing apparatus. In these situations it was desirable to get the pacemaker refractory periods at a length to insure that such retrograde depolarizations would not be detected. There was no device capable of determining the status of programmed refractory periods in respect to an ECG readout other than by doing extensive diagnostic interpretations of many ECG tapes.
In the past, there has also not been any quick and easy method by which a physician could display cardiac events in conjunction with an ECG wave pattern, such that both were synchronized in time. Such display of the cardiac events over the portion of the ECG wave pattern where it took place was not possible. Additionally, in situations where there were arrhythmias or other unnatural pacing problems, there were no devices capable of determining whether the events were truly what they appeared to be on the ECG wave pattern.
When this was the situation and the evaluation of the ECG tape was not in real time, the patient, if his pacing apparatus is not functioning properly, could possible die because there was not a quick evaluation in real time of what was going on. Therefore, because of the physician's inability to conduct such real time evaluations on a visual display, there could not be an effective evaluation of the proper or improper functioning of a cardiac pacing apparatus that was implanted.
These and others problems are solved by the apparatus of this invention.